(1) Field of the Invention
The invention relates to a light-sensitive, film-forming polymer useful in making a photographic element, having increased resistance to acids.
(2) State of the Prior Art
Photoresist polymers have been developed containing poly(vinyl cinnamate). An early resist lacquer comprising the homopolymer derived by esterifying poly(vinyl alcohol) with cinnamoyl chloride in pyridine is disclosed in U.S. Pat. No. 2,610,120 and U.S. Pat. No. 2,690,966. The resist polymer has been modified by coesterifying the poly(vinyl alcohol) with other acid compounds, such as dibasic or monobasic phenyl acid salts, as described, for example, in U.S. Pat. No. 2,861,058 and U.S. Pat. No. 3,560,465, respectively, in addition to a cinnamoyl chloride. Further, the cinnamate moiety has been modified by providing for certain substituents on the phenyl radical, as in the aforesaid U.S. Pat. No. 2,861,058. A photoresist is further taught in U.S. Pat. No. 3,696,072 wherein the vinyl cinnamate polymer is further modified by a second ethylenically unsaturated group in conjugation with the unsaturated sites of the cinnamate moiety.
Publications relating to the general background of photo-sensitive polymers include U.S. Pat. No. 3,821,167; Defensive Publication T-900,009; U.S. Pat. No. 2,725,372; British Patent Specification No. 1,353,506; East German Pat. No. 59,237; and Canadian Pat. No. 986,778.
All of the afore-described photoresists provide resistance to acid etches to varying degrees, depending largely on the corrosiveness of the acid used. Because of new high speed etching techniques for materials such as magnesium, photoresists having increased resistance to acids are needed. What is desired then is polymers having increased resistance, when photocrosslinked, to particularly corrosive etches, such as hot nitric acid, so that deep etching can be achieved more quickly without sacrificing image quality.